In certain industries, production processes and testing are carried out inside sealed vessels. The vessels may be held under specific pressure or temperature, or may contain a specific gas, liquid or solid. For example, a process may occur at an elevated or reduced temperature, at an elevated or reduced pressure and/or in the presence of an ambient gas. In some cases the contents inside the vessel may be delicate or sensitive and cannot be subject to contact with particles in the ambient environment. On the other hand, contents inside the vessel may be hazardous and must be contained within the vessel. Nonetheless, in some instances, access of the contents of the vessel may be necessary during the process or testing. Accordingly, a wall of the vessel may include an opening allowing access to the inside during the process or testing.
In many instances the opening to a vessel is a complex valve that prevents leakage from or into the vessel. Many valves include intricate parts and small crevices, such as threading, which gather material during a process or testing. Frequently, despite best efforts, the material is not entirely removed from these parts or crevices. As a result, such parts and crevices become contamination sites. A small contamination site holding material from a prior process or test in the vessel can jeopardize the next test or process entirely. Accordingly, it is desirable that an opening into a vessel be limited in its number of potential contamination sites.